If you were to remove the mitochondria from a eukaryotic cell, which (if any) of the following stages of cellular respiration could still occur?

Question

BlackTom AI · Accepted Answer

Glycolysis occurs in the cytosol, so it can still proceed even if mitochondria are removed.

Relevant concepts:
- Cellular respiration in eukaryotes has distinct stages with specific subcellular locations: glycolysis (cytosol), pyruvate oxidation and the citric acid (Krebs) cycle (mitochondrial matrix), and the electron transport chain/oxidative phosphorylation (inner mitochondrial membrane).
- Enzymes and membrane complexes required for pyruvate oxidation, the citric acid cycle (CAC), and the electron transport chain (ETC) are housed in mitochondria and depend on mitochondrial structures (e.g., PDH complex, CAC enzymes, respiratory complexes I–IV and ATP synthase).

Step-by-step reasoning:
1. Glycolysis: a ten-step pathway converting glucose to 2 pyruvate, producing a net 2 ATP and 2 NADH. All glycolytic enzymes are cytosolic, so these reactions do not require mitochondria and will continue if the cell has substrates and NAD+ available.
2. Pyruvate oxidation: in eukaryotes pyruvate is transported into mitochondria and converted to acetyl-CoA by the pyruvate dehydrogenase complex inside the mitochondrial matrix. Without mitochondria, this transport and enzyme complex are absent, so pyruvate oxidation cannot occur.
3. Citric acid cycle: CAC enzymes are located in the mitochondrial matrix and require acetyl‑CoA to operate. Without mitochondria there is no site or enzyme machinery for the CAC.
4. Electron transport chain: ETC complexes are embedded in the inner mitochondrial membrane; they create a proton gradient for oxidative phosphorylation. Without mitochondria there is no ETC or ATP synthase machinery.

Why d is correct and the others are incorrect:
- a (Pyruvate oxidation): incorrect because it requires mitochondrial import and the PDH complex.
- b (Citric acid cycle): incorrect because CAC enzymes are in the mitochondrial matrix.
- c (Electron transport chain): incorrect because ETC complexes are located in the inner mitochondrial membrane.
- d (Glycolysis): correct because glycolysis occurs in the cytosol and does not require mitochondrial structures.

Conclusion: Only glycolysis (option d) could still occur if mitochondria were removed; this matches the provided answer.

If you were to remove the mitochondria from a eukaryotic cell, which (if any) of the following stages of cellular respiration could still occur?单项选择题

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